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RETIREMENT AND POSTRETIREMENT PLANS - Dime KSOP Plan - BMP and Outside Director Retirement Plan (Details) - USD ($) | 3 Months Ended | 6 Months Ended
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Jun. 30, 2021 | Mar. 31, 2021 | Jun. 30, 2022 | Jun. 30, 2021
Dime KSOP Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contribution plan cost | $ 0 |  |  | $ 0
BMP and Outside Director Retirement Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Termination Age of Board Members |  |  | 75 years |
Curtailment loss |  | $ 1,500,000 |  |
Outside Director Retirement Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Obligation |  | 2,800,000 |  |
Board Member Retirement Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Obligation |  | $ 6,200,000 |  |

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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 + Details
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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